Primary tumors of orbital bone are rare, constituting up to 2% of all orbital masses.1 Chondromyxoid fibroma (CMF) is one of the least common tumors of bone, composing less than 1% of bone tumors and less than 2% of benign bone tumors.2,3 Apart from brief case reports,4- 6 orbital CMF has not been clearly documented in the ophthalmic literature. To our knowledge, we report for the first time the clinicopathological features and management options of an orbital CMF arising from the frontal bone.

Report of a Case

A 37-year-old woman had slowly progressive swelling of the left upper eyelid temporally associated with occasional headache and shooting pain for 3 years. On examination, visual acuity was 20/20 OU. The left eye showed 4 mm of proptosis with downward displacement, mild blepharoptosis, and choroidal folds at the posterior pole (Figure 1A). Computed tomography disclosed a superotemporal, noninfiltrative orbital mass with erosion of the adjacent frontal bone (Figure 1B and C). Differential diagnosis included lacrimal gland tumors, atypical dermoid cysts, and benign fibro-osseous lesions such as osteoma, fibrous dysplasia, or ossifying fibromyxoid tumor of soft parts.

The patient underwent transcutaneous extraperiosteal orbitotomy. Intraoperatively, the periosteum was separated by blunt dissection from the bone in the peripheral portions of the mass both superiorly and inferiorly. The mass proved to be located mainly in the extraperiosteal space, pushing the inferior and medial periosteal border into the orbital soft tissue. The tumor centrally showed a close connection to the bony wall. En bloc resection including the tumor, surrounding periosteum, and adjacent bony wall was performed.

Macroscopically, the mass measured 20 × 15 × 7 mm. Histopathological examination revealed a CMF (Figure 2A-C). The soft-tissue mass was surrounded inferomedially by periosteum. The periosteum showed calcification superiorly and laterally corresponding to the radio-dense margins on the computed tomographic scan. The lateral borders of the mass consisted of bone. The cellular elements displaying a low proliferation rate (MIB-1 < 1%) were positive for S-100B protein in the central chondroid area and positive for vimentin and smooth muscle actin in the peripheral fibroblastic area but negative for desmin, CD68, CD34, and CD31. Ultrastructural findings (Figure 2D and E) supported the diagnosis of CMF.

Postoperatively, recovery was fast and unremarkable. Two years after surgery, the patient showed marked improvement of proptosis, downward displacement, and blepharoptosis without evidence of recurrence or metastasis (Figure 1D).

Comment

Chondromyxoid fibroma manifests most frequently in the second and third decades of life, more often in males than in females.2,3 The long bones are the most common site, followed by the flat bones and the bones of the hands and feet.3 Craniofacial involvement is relatively rare.3 Histopathological differential diagnosis includes chondrosarcoma, enchondroma, or chordoma.2

Chondromyxoid fibroma with orbital involvement has been reported only in brief case reports.4- 6 Hashimoto et al4 and Cruz et al5 described a CMF of the ethmoid sinus destroying the medial orbital wall. Wolf et al6 reported an intracranial CMF of the frontal-sphenoid junction with secondary orbital involvement. In our patient, there was—to our knowledge for the first time—marked downward displacement and indentation of the globe with choroidal folds caused by progressive orbital tumor growth. Because the adjacent periosteum was intact, we elected to take an extraperiosteal approach, separating tumor and periosteum from bone as much as possible. In the area of close adhesion to the adjacent frontal bone, an en bloc resection including the tumor, surrounding periosteum, and adjacent bony wall was performed. Complete en bloc resection is important regarding both histopathological diagnosis and the prevention of tumor recurrence. Simple curettage may favor underdiagnosis and explain in part why the entity has been rarely documented.

In conclusion, CMF should be considered as a rare benign lesion in the differential diagnosis of primary orbital bone tumors.